Log Decay Study

Overview

Fallen trees are an important part of the forest ecosystem that persist over long periods of time. The Log Decay project investigates large fallen trees, the biodiversity that depend on them, and their future on the landscape.

Scope

This study examines the role of log size on the decomposition process, decay rates and associated biodiversity. Large logs produced from mature trees are expected to become scarcer in the production forestry estate where the harvest cycle is 100 years or less and may not adequately provide for the decay process and associated biodiversity unless mitigation measures are used. This and other studies at Warra are being done to inform on the formulation of such mitigation measures.

In 1998, twelve E. obliqua trees, six mature (130-220 cm diameter) and six regrowth (35-65 cm diameter), were felled within a multi-aged forest adjacent to the western boundary of coupe (Blakes) BK001B. The condition (wounds, decay etc) of each log and the local vegetation surrounding each log was assessed at the time of felling. Five log emergence traps have been fitted to each log. Each of these traps enclose a 3-metre section of log. The traps comprise of an aluminium frame to support a shadecloth tent sealed to the log and fitted with three exit holes leading to collection bottles – one at the highest and two at the lowest points of the tent on either side of the log. The tents can be removed to expose the 3-metre section of log for colonisation by invertebrates etc at set periods of time. The tents are re-fitted at intervals allowing invertebrates that colonised the log section when it was exposed to be collected.

Long Term Research

Two cycles of “exposed” and “closed”, each cycle spanning five years, have been done since the study commenced. The traps are currently open.

All samples collected from the emergence traps have been processed. All beetles within the samples have been sorted and identified. Those beetles are housed in the Tasmanian Forest Insect Collection located at the Tasmanian Museum and Art Gallery.